Abstract ? Administrative Core The Administrative (Admin) Core provides leadership and administrative support to achieve the overall Center aims and the aims of the individual Cores. The Admin Core will integrate and manage activities across Cores and work to foster transdisciplinary synergy across investigators. Centralized resources and assistance will be provided to facilitate project functions and the Core will ensure that the Center is a resource to the field and all those working to End HIV/AIDS among PWUD. In addition to supporting the Research Base, the Core will stimulate cross-Core exploratory initiatives to enhance support for investigators working in other US and international settings where high- incidence HIV outbreaks are occurring. The Specific Aims of the Admin Core are to (1) Provide scientific leadership and coordinate activities; (2) Foster transdisciplinary efforts to end HIV/AIDS among PWUD; (3) Provide centralized resources for project activities; and (4) Ensure that the Center serves as a resource to the field. These aims will be accomplished with several advisory structures including our affiliated investigators, a Leadership Group of members of all the Research Support Cores, and a Scientific Advisory Board.